Radio communication

Communication between planets within the galaxy, comes in a variety of forms. The most commonly used for non essential communication is radio waves. Most inhabited planets have at least one satelite orbiting them which act as giant radio antenna for sending and receiving radio signals. The planets surface will then have a system of signal towers which relay the signals from the satelites around the planet.
Due to a recent development in technology these radio signals can be boosted immensely making radio communication between planets within a solar system, near instantaneous. Communication between solar sytems can still take anywhere from a few hours to a couple of days, depending on distance. The Planetary Alliance maintain a relay system of satelites between solar systems in order to facillitate communication for everyone within the Alliance.
Faster than light communication does exist, but it is still limited, and expensive to maintain. As a result all non-essential communication is kept to radio waves, this includes most civillian communication.